in the term lac operon, the prefix 'lac' specifically refers to lactose . The lac operon is a transcriptionally regulated system in bacteria where a polycistronic structural gene is regulated by a common promoter and regulatory genes . It consists of genes responsible for the metabolism of lactose, which also acts as the inducer to regulate the switching on and off of the operon . Understanding these fundamental molecular mechanisms is a high-priority strategy for medical aspirants, as NCERT textbooks serve as the primary source for approximately 95% of NEET Biology questions .